The present invention relates generally to energy storage systems, and more specifically, to an energy storage system and method for direct coupling an energy storage unit and a power source.
Electric power conversion devices and associated control systems may be used to interface various energy resources. For example, a power system may include a variety of interconnected distributed energy resources (e.g., power generators and energy storage units) and loads. The power system may be referred to as a microgrid system, and may connect to a utility grid or another microgrid system. The power system employs the electric power conversion to convert power between these energy resources (e.g., AC/DC, DC/DC, AC/AC and DC/AC).
Power systems may be designed to supply power, regulate power and transfer power from one source to another with the goal of providing power to a load. It is desirable to provide power in the most efficient manner possible to maximize energy generation at the lowest cost. However, topology limitations and design requirements can be limitations on energy generation and the amount of power that is ultimately available for use.
An energy storage system is a power system in which at least one of the energy resources is an energy storage unit (e.g., battery energy storage or flywheel energy storage). Often, in the energy storage system, the energy storage unit stores energy from a renewable energy source, such as solar panels or wind. However, energy from a grid, such as a utility grid or another microgrid, is often available for storage in energy storage units.
When the power source of an energy storage system is a renewable source such as wind energy or solar energy, multiple power converters can be employed to supply energy to loads in an efficient manner. The power converters may include power inverters to convert the power supplied by the renewable source to alternating current (AC) for supplying the power to, e.g., an AC grid and/or AC loads, and DC/DC converters to convert the power supplied by the renewable source to, e.g., DC loads and/or energy storage units such as batteries or flywheels. Although these power converters can be utilized in a manner that allows for efficient transmission of power, the power converters themselves can be expensive, require expertise and time to implement in the field, and require a certain amount of space to implement.